The argument about contractions fails to take into account that, when you assume a large age, like 100,000 years, then the few years of negative growth become even more insignificant when looking at the aggregate growth rate. If we were only 5,000 years old, then the periods you cite are significant, but at 100,000 years old, a century or two of negative growth is negligible.
You are very obviously taking the assumed compound average of population increase for the recent and the early time periods and applying it to the earlier time periods when he actual rates were substantially less than 1 percent or negative percentages for centuries at a time. The population rates of the most most recent centuries and millenia are far higher than those of the earliest periods, so they are not representative of the early periods. Using the average of the entire period grossly distorts the final product of those calculations In other words, it is an elementary school level failure in basic mathematics.